Electronic cameras, video cameras, and related image capture devices have become very popular in recent years. This is at least in part due to the rapid advancements in electronic technology, reducing the cost of these devices and greatly enhancing their technical features. The combination of drastically reduced cost and greatly increased utility has driven consumer demand to unparalleled levels, making these devices very common among the general consumer population.
Traditionally, video capture devices were much more sophisticated and expensive than image capture devices, and electronic equipment needed to capture video was much more expensive than equipment for capturing still frames. This is in part because video generally requires 60 or more images per second, and traditional electronics capable of capturing and processing images this quickly were large and expensive. However, as high speed image processing electronics have become smaller, less expensive and easier to manufacture, both cameras and video cameras commonly include both image capture and video capture capabilities, lessening the practical and technological distinctions between these devices.
High speed image processing involves faster hardware, including processors and memory, as well as higher clock speeds. These requirements extend to the image sensor, which captures and outputs image information at a rate at least equal to the video frame rate, as well as the image processing electronics, which converts the output image information into a usable form for graphical display at similar rates. A general rule in electronics is that faster signal processing, particularly analog signal processing, consumes more electronic power. In addition, as image capture devices transition to high definition imaging, the graphical resolutions increase greatly. Increased resolution involves the capture and processing of more information than low resolution systems, further increasing power consumption. In some cases, digital electronics can both reduce power consumption and increase processing speeds, providing advantages over analog devices.
State of the art digital cameras still comprise analog equipment. For instance, an image sensor comprises a photodetector array that captures optical information at a given resolution, and outputs electronic information in analog form. In a column-parallel sensor, analog electronic signals are generally aggregated for each column and output to an analog to digital converter (ADC), also referred to as a column-parallel ADC. Several types of column-parallel ADCs exist, such as the slope-based ADC used in many modern state of the art image sensors. The column-parallel slope-based ADC provides desirable features, including compact implementation in the image sensor column.
One of the simpler and more common slope-based ADCs is referred to as a one-step single-slope (SS) ADC. The SS ADC utilizes a comparator and digital counter in each column of a photodetector array. The primary drawback is difficulty in scaling up to higher resolutions. This translates to a corresponding increase in conversion time or required clocking frequency for the ADC. However, as demand for higher resolutions continues with high definition video, further research and development in image processing electronics will be required. Higher resolutions, coupled with higher clock frequencies and lower power consumption are still being sought to meet the high definition requirements in modern electronics.